> Is there a preferred method/tool among developers of MPI-library for checking the count of the packets transmitted by the network card during two-sided communication?
>
> Is the use of
> iptables -I INPUT -i eth0
> iptables -I OUTPUT -o eth0
>
> recommended ?

If you're using an ethernet, non-OS-bypass transport (e.g., TCP), you might also want to look at ethtool.

Note that these counts will include control messages sent by Open MPI, too -- not just raw MPI traffic. They also will not include any traffic sent across shared memory (or other transports).